1. Field of the Invention
The present invention relates to a class of porous metal organic materials has novel selective adsorption characteristics and for methods of making and using same.
More particularly, the present invention relates to a class of porous metal organic materials has novel selective adsorption characteristics, where materials are based on trans linked chains of metal oxygen octahedra that are cross-linked by aromatic dicarboxylic acids and for methods of making and using same.
2. Description of the Related Art
Many applications of nanoporous materials such as molecular sieving, ion exchange and functional nanocomposites are based on specific interactions between the host frameworks and removable guest species. The capacity and selectivity of nanoporous materials in absorption and in separation of molecular mixtures depend on specific interactions between the host frameworks and removable guest species and in some cases the degree to which the structure of the host lattice can relax as molecular species are intercalated. Detailed structural data are critical to understand these interactions.
The classical zeolite frameworks are relatively rigid and exhibit little deformation upon loading and unloading of various guest species.1 On the other hand, intercalation into layered structures leads to expansion of the interlayer separation because of the very weak interlayer bonding, and can lead to complete exfoliation of the layers.2 
Variable flexibilities without loss of crystallinity are expected for structures containing rigid building blocks linked by relatively deformable hinge-like units. Examples of framework flexibility have been found in a number of metal-organic frameworks (MOFs).3 Among them, a group of compounds first reported by Férey and coworkers,4 based on chains of trans corner-sharing octahedra MO6 (M=V,4 Cr,5 Al,6 Fe,7 In8) cross-linked by 1,4-benzene dicarboxylate (BDC) upon removal or absorption of guest species show remarkable framework flexibility. The first member of the group [V(OH)BDC](H2BDC)x was designated as MIL-47as.4 The guest H2BDC molecules are removed on heating in air and the V3+ ions are oxidized to V4+ without changing the framework topology. The product, VOBDC (designated MIL-47) was observed to absorb different small guest molecules. No structural information on the absorbed guest molecules is available although the structure of MIL-47 was solved from single crystal data.4 
Sorption studies of these metal organic frameworks have focused on H2 adsorption,9 but some studies of the absorption of CO210 and CH411 have been reported. Of particular relevance to this work is the paper by Férey and coworkers on the adsorption of CH4 and CO2 by MOHBDC (M=Cr, Al) and VOBDC.11a The V(IV) phase VOBDC shows some differences in the absorption isotherms compared with the trivalent compounds, but the amounts of CO2 adsorbed above 10 bar are comparable. The relatively weak enthalpy of adsorption suggested that VOBDC has no specific adsorption sites for CO2.11a 
Thus, there is a need in the art for improved absorbants or absorbents, especially for sulfur containing compounds.